once again, chris cuomo as "20/20" continues with tragedy at the elementary school. Imagine getting a phone call or a text just minutes after your kid went to elementary school and it read, lock down. And you start hearing about the shooting. That was the reality this morning for paints as they raced to the cars to the sandy hook elementary school, saying this cannot be happening here, to us. A school of nearly 700 student, k through fourth grade, nationally known for academic achievement and yet all of the worst things we can imagine did happen here, did happen in the school. Here is jim avila with a look at the school that will never be the same again. Sandy hook elementary has always been well known here in central connecticut. Not for tragedy but a warm sanctuary for children 5 to 10 years old. And small classes of 20. Known for its caring teachers and scoring a perfect ten from gradeschools.Org. The top 3% of elementary schools. People come to newtown for the schools. The husbands will sacrifice the commute just to live in newtown. It's farther than anyone else. The award winning principal dawn hochsprung. Two days ago, she wrote, sandy hook stu enjoy the concert. And the extra work that teach rers doing at sandy hook. 30 teachers gather for an early morning happy hour. And this tweet, safety first at sandy hook. It's a beautiful day for our anal evacuation drill. Welcoming in coming kindergartners, this fall. 74 opportunities to inspire life long learning. We have to say the teachers are pretty much where it's at. They love the kids. They love to teach and the kids get a lot of of them. Caitlin remembers the warmth she felt at the school. I felt it was the best but I'm biassed. What was special about it it's close knit. It's a small school but I don't notch it was really important to me and my development. Katelin watched the tragedy unfold on television this morning. Heard little children attending the same classrooms. Hiding in close sets and corners. I know the layout of the school so I can imagine what was going on, the chaos. So this is really, really close to home. Sandy hook is quaint. Idealic. Just this year, they put? A security plan makes it mandatory for visitors to ring a doorbell. And in staff don't recognize the visitor, they had to present a prikt id, sign in and only then be let in the school. You hauls to press a button and ask who you are. I don't know how anyone could just walk in. When kate lint went to sandy hook there were emergency drills. What the kids are saying in the news, go in the corner of the room, they shut off the light, we had to be quiet, not talk, which is hard for a kid when they think it's not real. Buff I think most of them know that something was really serious this time.

This transcript has been automatically generated and may not be 100% accurate.

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